Adds parameter_bounds to persisted info

Adds handling for storage/retrieval of parameter data bounds so they do not need to be calculated at the time of the request.  Bounds are updated as data is added to a parameter and stored in the persistence layer for rapid retrieval across coverage loads.
Moves data bounds into *Value classes

Calculation / updating of bounds information moved down into *Value classes.  This allows each distinct type of Value class to handle it's data bounds, which greatly reduces complexity
Merge pull request #32 from blazetopher/bounds_update

Bounds update